1835.] LINES OF VIBRATION. 307 



offended stopped tlie volcano of xVntuco. This silly belief is 

 curious, because it shows that experience has taught them to 

 observe, that there exists a relation between tlie suppressed action 

 of the volcanos, and tlie trembling- of the ground. It was neces- 

 sary to apply the witclicraft to the point where their perception 

 of cause and effect failed ; and this was the closing of tiie volcanic 

 vent. This belief is the more singular in this particular instance, 

 because, according to Captain Fitz Roy, there is reason to believe 

 that Antuco was noways affected. 



The town of Concepcion was built in the usual Spanish 

 fashion, w ith all the streets running at right angles to each other ; 

 one set ranging S.W. by W., and the other set N.W. by N. 

 The walls in the former direction certainly stood better than 

 those in the latter : the greater number of the masses of brick- 

 work were thrown down towards the N.E. Both these cir- 

 cumstances perfectly agree with the general idea, of the undula- 

 tions havinor come from theS.^T. ; in whicii Quarter subterranean 

 noises were also heard : for it is ev"dent that the walls running 

 S.W. and N.E. Avhich presented their ends to the point whence 

 the undulations came, would be much less likely to fall than 

 those walls which, running N.W. and S.E., must in their whole 

 lengths have been at the same instant thrown out of the per- 

 pendicular ; for the undulations, coming from the S.W., must 

 have extended in N.W. and S.E. waves, as they passed under the 

 foundations. This may be illustrated by placing books edgeways 

 on a carpet, and then, after the manner suggested by Michell, 

 imitating the undulations of an earthquake: it will be found that 

 thev fall with more or less readiness, accordinor as their direction 

 more or less nearly coincides with the line of the waves. The 

 fissures in the ground generally, though not uniformly, extended 

 in a S.E. and N."W. direction ; and therefore corresponded to the 

 lines of undulation or of principal flexure. Bearing in mind all 

 these circumstances, which so clearly point to the S.W. as the 

 chief focus of disturbance, it is a very interesting fact that the 

 island of S. Maria, situated in that quarter, was, during the 

 general uplifting of the land, raised to nearly three times the 

 height of any other part of the coast. 



The different resistance offered by the walls, according to their 

 direction, was well exemplified in the case of the Cathedral. 



